1. Field of the Invention
The present invention relates to a reproducing apparatus such as a high definition digital versatile disc (HD-DVD) player.
2. Description of the Related Art
In recent years, with a progress in digital compression-encoding technology for motion video, reproducing apparatuses (players), which can handle high-definition video according to the high definition (HD) standard, have steadily been developed.
In this type of player, there is a demand for blending video data and graphics data at a high level, thereby to enhance interactivity. Alpha blending is known as a technique for blending picture data. The alpha blending is a blending technique wherein alpha data, which represents the degree of transparency of each pixel of a picture, is used to overlay this picture on another picture.
Japanese Patent Application KOKAI Publication No. 8-205092, for instance, discloses a system in which graphics data and video data are mixed by a display controller. In that system, the display controller captures video data and overlays the captured video data on a partial area of a graphics screen.
The system of Japanese Patent Application KOKAI Publication No. 8-205092, however, presupposes that video data with a relatively low resolution is handled. In that system, no consideration is given to the handling of high-definition pictures such as HD-standard video data. The amount of HD-standard video data, which is to be processed per unit time, is enormous, and it is practically difficult for the display controller to capture HD-standard video data.
It is thus desirable to realize a system architecture wherein video data, which is output from, e.g., a video decoder, and graphics data, which is output from a display controller, are blended not within the display controller, but by an external blending circuit.
In normal cases, the alpha blending process is executed on an RGB color space. Thus, when video data of a YUV color space and graphics data of an RGB color space are to be blended, the video data is once color-converted to RGB data, and then blended with the graphics data. In this case, a color distortion occurs due to a rounding error at a time of a color conversion arithmetic operation. Consequently, the image quality of HD-standard video data deteriorates due to the blending process.
Under the circumstances, there is a demand for a reproducing apparatus that can blend video data and graphics data without degrading the image quality of video data.